/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;

import java.util.Arrays;
import java.util.Comparator;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link BiMap} whose contents will never change, with many other important properties detailed
 * at {@link ImmutableCollection}.
 *
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public abstract class ImmutableBiMap<K, V> extends ImmutableBiMapFauxverideShim<K, V>
        implements BiMap<K, V>
{

    /**
     * Returns a {@link Collector} that accumulates elements into an {@code ImmutableBiMap} whose keys
     * and values are the result of applying the provided mapping functions to the input elements.
     * Entries appear in the result {@code ImmutableBiMap} in encounter order.
     *
     * <p>If the mapped keys or values contain duplicates (according to {@link Object#equals(Object)},
     * an {@code IllegalArgumentException} is thrown when the collection operation is performed. (This
     * differs from the {@code Collector} returned by {@link Collectors#toMap(Function, Function)},
     * which throws an {@code IllegalStateException}.)
     *
     * @since 21.0
     */
    public static <T extends @Nullable Object, K, V>
    Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
            Function<? super T, ? extends K> keyFunction,
            Function<? super T, ? extends V> valueFunction)
    {
        return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
    }

    /**
     * Returns the empty bimap.
     *
     * <p><b>Performance note:</b> the instance returned is a singleton.
     */
    // Casting to any type is safe because the set will never hold any elements.
    @SuppressWarnings("unchecked")
    public static <K, V> ImmutableBiMap<K, V> of()
    {
        return (ImmutableBiMap<K, V>) RegularImmutableBiMap.EMPTY;
    }

    /**
     * Returns an immutable bimap containing a single entry.
     */
    public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1)
    {
        return new SingletonImmutableBiMap<>(k1, v1);
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     */
    public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2)
    {
        return RegularImmutableBiMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     */
    public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3)
    {
        return RegularImmutableBiMap.fromEntries(entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     */
    public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4)
    {
        return RegularImmutableBiMap.fromEntries(
                entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     */
    public static <K, V> ImmutableBiMap<K, V> of(
            K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5)
    {
        return RegularImmutableBiMap.fromEntries(
                entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4), entryOf(k5, v5));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     * @since 31.0
     */
    public static <K, V> ImmutableBiMap<K, V> of(
            K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6)
    {
        return RegularImmutableBiMap.fromEntries(
                entryOf(k1, v1),
                entryOf(k2, v2),
                entryOf(k3, v3),
                entryOf(k4, v4),
                entryOf(k5, v5),
                entryOf(k6, v6));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     * @since 31.0
     */
    public static <K, V> ImmutableBiMap<K, V> of(
            K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5, K k6, V v6, K k7, V v7)
    {
        return RegularImmutableBiMap.fromEntries(
                entryOf(k1, v1),
                entryOf(k2, v2),
                entryOf(k3, v3),
                entryOf(k4, v4),
                entryOf(k5, v5),
                entryOf(k6, v6),
                entryOf(k7, v7));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     * @since 31.0
     */
    public static <K, V> ImmutableBiMap<K, V> of(
            K k1,
            V v1,
            K k2,
            V v2,
            K k3,
            V v3,
            K k4,
            V v4,
            K k5,
            V v5,
            K k6,
            V v6,
            K k7,
            V v7,
            K k8,
            V v8)
    {
        return RegularImmutableBiMap.fromEntries(
                entryOf(k1, v1),
                entryOf(k2, v2),
                entryOf(k3, v3),
                entryOf(k4, v4),
                entryOf(k5, v5),
                entryOf(k6, v6),
                entryOf(k7, v7),
                entryOf(k8, v8));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     * @since 31.0
     */
    public static <K, V> ImmutableBiMap<K, V> of(
            K k1,
            V v1,
            K k2,
            V v2,
            K k3,
            V v3,
            K k4,
            V v4,
            K k5,
            V v5,
            K k6,
            V v6,
            K k7,
            V v7,
            K k8,
            V v8,
            K k9,
            V v9)
    {
        return RegularImmutableBiMap.fromEntries(
                entryOf(k1, v1),
                entryOf(k2, v2),
                entryOf(k3, v3),
                entryOf(k4, v4),
                entryOf(k5, v5),
                entryOf(k6, v6),
                entryOf(k7, v7),
                entryOf(k8, v8),
                entryOf(k9, v9));
    }

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are added
     * @since 31.0
     */
    public static <K, V> ImmutableBiMap<K, V> of(
            K k1,
            V v1,
            K k2,
            V v2,
            K k3,
            V v3,
            K k4,
            V v4,
            K k5,
            V v5,
            K k6,
            V v6,
            K k7,
            V v7,
            K k8,
            V v8,
            K k9,
            V v9,
            K k10,
            V v10)
    {
        return RegularImmutableBiMap.fromEntries(
                entryOf(k1, v1),
                entryOf(k2, v2),
                entryOf(k3, v3),
                entryOf(k4, v4),
                entryOf(k5, v5),
                entryOf(k6, v6),
                entryOf(k7, v7),
                entryOf(k8, v8),
                entryOf(k9, v9),
                entryOf(k10, v10));
    }

    // looking for of() with > 10 entries? Use the builder or ofEntries instead.

    /**
     * Returns an immutable map containing the given entries, in order.
     *
     * @throws IllegalArgumentException if duplicate keys or values are provided
     * @since 31.0
     */
    @SafeVarargs
    public static <K, V> ImmutableBiMap<K, V> ofEntries(Entry<? extends K, ? extends V>... entries)
    {
        @SuppressWarnings("unchecked") // we will only ever read these
        Entry<K, V>[] entries2 = (Entry<K, V>[]) entries;
        return RegularImmutableBiMap.fromEntries(entries2);
    }

    /**
     * Returns a new builder. The generated builder is equivalent to the builder created by the {@link
     * Builder} constructor.
     */
    public static <K, V> Builder<K, V> builder()
    {
        return new Builder<>();
    }

    /**
     * Returns a new builder, expecting the specified number of entries to be added.
     *
     * <p>If {@code expectedSize} is exactly the number of entries added to the builder before {@link
     * Builder#build} is called, the builder is likely to perform better than an unsized {@link
     * #builder()} would have.
     *
     * <p>It is not specified if any performance benefits apply if {@code expectedSize} is close to,
     * but not exactly, the number of entries added to the builder.
     *
     * @since 23.1
     */
    @Beta
    public static <K, V> Builder<K, V> builderWithExpectedSize(int expectedSize)
    {
        checkNonnegative(expectedSize, "expectedSize");
        return new Builder<>(expectedSize);
    }

    /**
     * A builder for creating immutable bimap instances, especially {@code public static final} bimaps
     * ("constant bimaps"). Example:
     *
     * <pre>{@code
     * static final ImmutableBiMap<String, Integer> WORD_TO_INT =
     *     new ImmutableBiMap.Builder<String, Integer>()
     *         .put("one", 1)
     *         .put("two", 2)
     *         .put("three", 3)
     *         .buildOrThrow();
     * }</pre>
     *
     * <p>For <i>small</i> immutable bimaps, the {@code ImmutableBiMap.of()} methods are even more
     * convenient.
     *
     * <p>By default, a {@code Builder} will generate bimaps that iterate over entries in the order
     * they were inserted into the builder. For example, in the above example, {@code
     * WORD_TO_INT.entrySet()} is guaranteed to iterate over the entries in the order {@code "one"=1,
     * "two"=2, "three"=3}, and {@code keySet()} and {@code values()} respect the same order. If you
     * want a different order, consider using {@link #orderEntriesByValue(Comparator)}, which changes
     * this builder to sort entries by value.
     *
     * <p>Builder instances can be reused - it is safe to call {@link #buildOrThrow} multiple times to
     * build multiple bimaps in series. Each bimap is a superset of the bimaps created before it.
     *
     * @since 2.0
     */
    public static final class Builder<K, V> extends ImmutableMap.Builder<K, V>
    {

        /**
         * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
         * ImmutableBiMap#builder}.
         */
        public Builder()
        {
        }

        Builder(int size)
        {
            super(size);
        }

        /**
         * Associates {@code key} with {@code value} in the built bimap. Duplicate keys or values are
         * not allowed, and will cause {@link #build} to fail.
         */
        @CanIgnoreReturnValue
        @Override
        public Builder<K, V> put(K key, V value)
        {
            super.put(key, value);
            return this;
        }

        /**
         * Adds the given {@code entry} to the bimap. Duplicate keys or values are not allowed, and will
         * cause {@link #build} to fail.
         *
         * @since 19.0
         */
        @CanIgnoreReturnValue
        @Override
        public Builder<K, V> put(Entry<? extends K, ? extends V> entry)
        {
            super.put(entry);
            return this;
        }

        /**
         * Associates all of the given map's keys and values in the built bimap. Duplicate keys or
         * values are not allowed, and will cause {@link #build} to fail.
         *
         * @throws NullPointerException if any key or value in {@code map} is null
         */
        @CanIgnoreReturnValue
        @Override
        public Builder<K, V> putAll(Map<? extends K, ? extends V> map)
        {
            super.putAll(map);
            return this;
        }

        /**
         * Adds all of the given entries to the built bimap. Duplicate keys or values are not allowed,
         * and will cause {@link #build} to fail.
         *
         * @throws NullPointerException if any key, value, or entry is null
         * @since 19.0
         */
        @CanIgnoreReturnValue
        @Beta
        @Override
        public Builder<K, V> putAll(Iterable<? extends Entry<? extends K, ? extends V>> entries)
        {
            super.putAll(entries);
            return this;
        }

        /**
         * Configures this {@code Builder} to order entries by value according to the specified
         * comparator.
         *
         * <p>The sort order is stable, that is, if two entries have values that compare as equivalent,
         * the entry that was inserted first will be first in the built map's iteration order.
         *
         * @throws IllegalStateException if this method was already called
         * @since 19.0
         */
        @CanIgnoreReturnValue
        @Beta
        @Override
        public Builder<K, V> orderEntriesByValue(Comparator<? super V> valueComparator)
        {
            super.orderEntriesByValue(valueComparator);
            return this;
        }

        @Override
        @CanIgnoreReturnValue
        Builder<K, V> combine(ImmutableMap.Builder<K, V> builder)
        {
            super.combine(builder);
            return this;
        }

        /**
         * Returns a newly-created immutable bimap. The iteration order of the returned bimap is the
         * order in which entries were inserted into the builder, unless {@link #orderEntriesByValue}
         * was called, in which case entries are sorted by value.
         *
         * <p>Prefer the equivalent method {@link #buildOrThrow()} to make it explicit that the method
         * will throw an exception if there are duplicate keys or values. The {@code build()} method
         * will soon be deprecated.
         *
         * @throws IllegalArgumentException if duplicate keys or values were added
         */
        @Override
        public ImmutableBiMap<K, V> build()
        {
            return buildOrThrow();
        }

        /**
         * Returns a newly-created immutable bimap, or throws an exception if any key or value was added
         * more than once. The iteration order of the returned bimap is the order in which entries were
         * inserted into the builder, unless {@link #orderEntriesByValue} was called, in which case
         * entries are sorted by value.
         *
         * @throws IllegalArgumentException if duplicate keys or values were added
         * @since 31.0
         */
        @Override
        public ImmutableBiMap<K, V> buildOrThrow()
        {
            switch (size)
            {
                case 0:
                    return of();
                case 1:
                    // requireNonNull is safe because the first `size` elements have been filled in.
                    Entry<K, V> onlyEntry = requireNonNull(entries[0]);
                    return of(onlyEntry.getKey(), onlyEntry.getValue());
                default:
                    /*
                     * If entries is full, or if hash flooding is detected, then this implementation may end
                     * up using the entries array directly and writing over the entry objects with
                     * non-terminal entries, but this is safe; if this Builder is used further, it will grow
                     * the entries array (so it can't affect the original array), and future build() calls
                     * will always copy any entry objects that cannot be safely reused.
                     */
                    if (valueComparator != null)
                    {
                        if (entriesUsed)
                        {
                            entries = Arrays.copyOf(entries, size);
                        }
                        Arrays.sort(
                                entries,
                                0,
                                size,
                                Ordering.from(valueComparator).onResultOf(Maps.<V>valueFunction()));
                    }
                    entriesUsed = true;
                    return RegularImmutableBiMap.fromEntryArray(size, entries);
            }
        }

        @Override
        @VisibleForTesting
        ImmutableBiMap<K, V> buildJdkBacked()
        {
            checkState(
                    valueComparator == null,
                    "buildJdkBacked is for tests only, doesn't support orderEntriesByValue");
            switch (size)
            {
                case 0:
                    return of();
                case 1:
                    // requireNonNull is safe because the first `size` elements have been filled in.
                    Entry<K, V> onlyEntry = requireNonNull(entries[0]);
                    return of(onlyEntry.getKey(), onlyEntry.getValue());
                default:
                    entriesUsed = true;
                    return RegularImmutableBiMap.fromEntryArray(size, entries);
            }
        }
    }

    /**
     * Returns an immutable bimap containing the same entries as {@code map}. If {@code map} somehow
     * contains entries with duplicate keys (for example, if it is a {@code SortedMap} whose
     * comparator is not <i>consistent with equals</i>), the results of this method are undefined.
     *
     * <p>The returned {@code BiMap} iterates over entries in the same order as the {@code entrySet}
     * of the original map.
     *
     * <p>Despite the method name, this method attempts to avoid actually copying the data when it is
     * safe to do so. The exact circumstances under which a copy will or will not be performed are
     * undocumented and subject to change.
     *
     * @throws IllegalArgumentException if two keys have the same value or two values have the same
     *                                  key
     * @throws NullPointerException     if any key or value in {@code map} is null
     */
    public static <K, V> ImmutableBiMap<K, V> copyOf(Map<? extends K, ? extends V> map)
    {
        if (map instanceof ImmutableBiMap)
        {
            @SuppressWarnings("unchecked") // safe since map is not writable
            ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
            // TODO(lowasser): if we need to make a copy of a BiMap because the
            // forward map is a view, don't make a copy of the non-view delegate map
            if (!bimap.isPartialView())
            {
                return bimap;
            }
        }
        return copyOf(map.entrySet());
    }

    /**
     * Returns an immutable bimap containing the given entries. The returned bimap iterates over
     * entries in the same order as the original iterable.
     *
     * @throws IllegalArgumentException if two keys have the same value or two values have the same
     *                                  key
     * @throws NullPointerException     if any key, value, or entry is null
     * @since 19.0
     */
    @Beta
    public static <K, V> ImmutableBiMap<K, V> copyOf(
            Iterable<? extends Entry<? extends K, ? extends V>> entries)
    {
        @SuppressWarnings("unchecked") // we'll only be using getKey and getValue, which are covariant
        Entry<K, V>[] entryArray = (Entry<K, V>[]) Iterables.toArray(entries, EMPTY_ENTRY_ARRAY);
        switch (entryArray.length)
        {
            case 0:
                return of();
            case 1:
                Entry<K, V> entry = entryArray[0];
                return of(entry.getKey(), entry.getValue());
            default:
                /*
                 * The current implementation will end up using entryArray directly, though it will write
                 * over the (arbitrary, potentially mutable) Entry objects actually stored in entryArray.
                 */
                return RegularImmutableBiMap.fromEntries(entryArray);
        }
    }

    ImmutableBiMap()
    {
    }

    /**
     * {@inheritDoc}
     *
     * <p>The inverse of an {@code ImmutableBiMap} is another {@code ImmutableBiMap}.
     */
    @Override
    public abstract ImmutableBiMap<V, K> inverse();

    /**
     * Returns an immutable set of the values in this map, in the same order they appear in {@link
     * #entrySet}.
     */
    @Override
    public ImmutableSet<V> values()
    {
        return inverse().keySet();
    }

    @Override
    final ImmutableSet<V> createValues()
    {
        throw new AssertionError("should never be called");
    }

    /**
     * Guaranteed to throw an exception and leave the bimap unmodified.
     *
     * @throws UnsupportedOperationException always
     * @deprecated Unsupported operation.
     */
    @CanIgnoreReturnValue
    @Deprecated
    @Override
    @DoNotCall("Always throws UnsupportedOperationException")
    @CheckForNull
    public final V forcePut(K key, V value)
    {
        throw new UnsupportedOperationException();
    }

    /**
     * Serialized type for all ImmutableBiMap instances. It captures the logical contents and they are
     * reconstructed using public factory methods. This ensures that the implementation types remain
     * as implementation details.
     *
     * <p>Since the bimap is immutable, ImmutableBiMap doesn't require special logic for keeping the
     * bimap and its inverse in sync during serialization, the way AbstractBiMap does.
     */
    private static class SerializedForm<K, V> extends ImmutableMap.SerializedForm<K, V>
    {
        SerializedForm(ImmutableBiMap<K, V> bimap)
        {
            super(bimap);
        }

        @Override
        Builder<K, V> makeBuilder(int size)
        {
            return new Builder<>(size);
        }

        private static final long serialVersionUID = 0;
    }

    @Override
    Object writeReplace()
    {
        return new SerializedForm<>(this);
    }
}
